Chlorofluorocarbons (CFCs) are known and widely used in the industry as solvents, blowing agents, heat transfer fluid, aerosol propellants, and for other uses. However, CFCs are also well-known to have ozone depletion potential (ODP) and are regulated by the Montreal Protocol. A suitable replacement material would have negligible or no ODP, as well as an acceptable global warming potential (GWP).
For example, 1-chloro-3,3,3-trifluoropropene (1233zd) is a chlorofluoroolefin with zero GWP and negligible ODP, which makes it very useful in foaming, aerosol and refrigeration applications. Cis-1233zd is much more preferred than its trans isomer (“trans-1233zd”) in solvent applications due to its higher boiling point. While various methods can be used to make 1233zd (see, e.g., U.S. Pat. No. 6,958,424, U.S. Pat. No. 6,844,475, U.S. Pat. No. 5,616,819, US 2008/0103342, WO 2010/059496), trans-1233zd is the thermal dynamically favored product in such conventional manufacturing processes, with only 3-5% of cis isomer being typically formed.
Some higher efficiencies have been achieved in the laboratory with the use of 3,3,3-trifluoropropyne (TFP) as a feedstock. The major problem with such protocols is that such TFP feedstocks are not available in large quantities. Accordingly, efforts have been made to improve TFP production processes, including efforts related to the use of the less desired trans-1233zd isomer.
For example, in one process trans-1233zd is treated with LDA (lithium diisopropylamide) or MeLi (methyl lithium) at −80° C. to obtain trifluoroacetylenic lithium salt (Eur. J. Org. Chem. 2009, 4395-4399), which can be hydrolyzed to TFP. This TFP lithium salt can also be obtained by deprotonating CF3CH2CHF2 (245fa) with n-butyl lithium (Organomet. 2003, 5534) in ether.
As an additional example, U.S. Pat. No. 8,791,309, describes a process using sodium amide as base for dehydrochlorination of trans-1233zd in ether or ammonia to produce 3,3,3-trifluoropropyne. However, such processes are expensive to implement on a commercial scale owing to operating conditions and/or the toxicity and/or hazardous nature of reactants.
Commercial processes for producing TFP not using trans-1233zd also have disadvantages. For example, 1,1,2-trichloro-3,3,3-trifluoropropene treated with zinc in DMF at 100° C. followed by hydrolysis with water can provide a 75% yield of TFP (J. Flu. Chem. 36(3), 313-17; 1987; J. Org. Chem. 1963, 28, 1139-40); however, the synthesis of 1,1,2-trichloro-3,3,3-trifluoro-propene requires a multiple step reaction, and is not commercially available in large quantities. Furthermore, the use of zinc in the process can lead to environmentally related expenses.
Accordingly, there remains a need to safely and economically produce TFP on a commercial scale.